The semiconductor chip packaging industry is a highly competitive business in which the packaging companies are waging an on-going battle to reduce the costs associated with packaging their own chips and, many times, the chips owned by other parties. New technologies are constantly being investigated in order to reduce the packaging cost while producing packaging structures and processes which produce similar or superior results. Further, there is on-going pressure from the electronic industry to reduce the internal impedances of semiconductor packages so that the semiconductor makers may increase the speed of their chips without experiencing significant signal degradation thereby decreasing the processing and/or response time a user of a finished electronic product will encounter when requesting the electronic product to perform a given task. Further still, the electronic industry requires that the chips are packaged in smaller and smaller form factors so that the packaged chips take up less space on a supporting circuitized substrate (such as a printed wiring board, "PWB"). It is also important that the thickness dimension of the packaged chips is reduced so that the same operational circuitry may be fit into a smaller area thereby allowing for more portability (size, weight, etc.) for the resulting finished electronic product and/or allowing for an increase in a product's processing power without also increasing its size. As the packaged chips are made smaller and placed closer and closer together on the PWB, the chips will produce more heat and will receive more heat from the adjacent chips. It is therefore also very important to provide a direct thermal path to facilitate the removal of heat from the packaged chips.
In response to industry concerns, pin grid array ("PGA") products, in which relatively large conductive pins attach the circuitry in a particular semiconductor package to the circuitry on the PWB, and other such large packaging conventions have been used less frequently in favor of smaller packaging conventions, such as ball grid array ("BGA") packages. In BGA packages, the aforementioned pins are typically replaced by solder balls thereby reducing the height of the packages from the PWB, reducing the area needed to package chips and further allowing for more elegant packaging solutions. The solder balls on a BGA device are generally either disposed in regular grid-like patterns, substantially covering the face surface of the packaged chip (commonly referred to as an "area array") or in elongated rows extending parallel to and adjacent each edge of the front surface of the packaged chip.
BGA and even smaller chip scale packaging ("CSP") technology refer to a large range of semiconductor packages which typically use interconnection processes such as wirebonding, beam lead, tape automated bonding ("TAB") or the like as an intermediate connection step to interconnect the chip contacts to the exposed package terminals. This results in a testable device prior to mechanical attachment to the bond pads on supporting substrate. The BGA/CSP packaged chips are then typically interconnected on a PWB using standard tin-lead solder connections.
Certain packaging designs have nicely met the above stated industry concerns. An example of such a design is shown in U.S. Pat. Nos. 5,148,265 and 5,148,266, the disclosures of which are incorporated herein by reference. In one embodiment, these patents disclose the use of a chip carrier in combination with a compliant layer to provide a cost efficient, low profile CSP.
Despite these and other efforts in the art, still further improvements in interconnection technology would be desirable.